As described in detail in the aforementioned U.S. Pat. No. 4,574,975, a number of prior art structures have been developed for the purpose of closing bottles and cans, whether of metal, plastic or glass, jars and others containers but few of such closure devices have been designed so that they can be refitted on a once opened container to reseal the dispensing opening and those that have had resealable features have often been difficult to manipulate by a user on the one hand, and, on the other, could not be usefully employed where the contents of the container were under pressure or were capable of generating pressure. This is of particular concern where a resealable closure is employed as there is always the possibility of injury where the closure device is improperly installed on the opening of the container unbeknown to the user. With the passage of time, pressure build-up can cause unexpected popping or "missileing" of the closure device which can result in injury to a user or bystander.
Another difficulty encountered in this field is the task of providing a closure that can be opened by the widest possible range of users. In this connection, a subsidiary but closely related problem is that of venting where the contents of the container are either at a vacuum or under pressure. In the former case, breaking the vacuum can make opening difficult particularly where any portion of a resealable closure acts as a plug in the container opening. In the latter case, internal pressure build-up can also force parts of the closure device to lock on the opening or an associated flange of the opening thus rendering it difficult for a number of users to remove the container closure. It is necessary, therefore, to provide a safe venting feature to any resealable container closure that is intended to be employed where the contents of the container will be at other than atmospheric pressure. The above-cited United States Patent refers to other criteria which resealable container closures must satisfy to enable them to be marketed in competition with other types of containers.
The present invention incorporates a number of the features of the aforementioned U.S. Pat. No. 4,574,975 but also provides an improved opening arrangement which will enable the closure device to be used on a container without regard to characteristics of the contents of the container.
In a preferred embodiment, the closure device for a can body is provided with a metallic end wall having an opening formed therethrough surrounded by an upwardly and outwardly flaring beaded flange of a structure similar to that disclosed in FIG. 11 of the aforementioned United States Patent. The flexible closure device which is preferably of molded plastic includes a central panel, a lever and a nose which acts as a connecting portion between the lever and the central panel substantially as in the embodiment described in the aforementioned U.S. Patent. In the present invention, the central panel has an inner annular skirt or ring portion which includes a peripheral surface which is spaced just inwardly of the interior surface of the beaded flange when the closure device is fitted on the beaded flange. The central panel is relieved or hollowed out in the area spaced inwardly of the peripheral surface of the ring portion so as to impart greater flexibility to the central panel especially during opening and closing of the end wall opening. With this arrangement, particularly where the contents of the container are under pressure, the peripheral surface of the ring portion will not normally engage to any significant extent the interior surface of the beaded flange when the closure device is fitted on the end wall to close the end wall opening. The nose portion located between the lever portion and the central panel engages the exterior of the beaded flange to retain the closure device in the opening of the end wall.
A pair of straps or handles are provided to facilitate lifting of the lever portion to commence removal of the closure device. In the present embodiment, with the lever portion in its downwardly extending position a user will pull on one of the straps or handles. Venting of the contents of the container such as a can body will commence as soon as a passage way is cleared between the outer surface of the flange and he nose portion. However, further pulling on the strap or handle will bring at least a portion of the peripheral surface of the ring portion into frictional engagement with a portion of the internal surface of the beaded flange to thereby provide resistance at least initially to further opening movement of the closure device. In this manner, relatively safe venting of the contents will occur while a retarding force is exerted by virtue of angular displacement of the ring portion. Additionally, flexing of the ring portion causes outward bulging of a section of the ring portion so that the adjacent peripheral surface engages the interior surface of the beaded flange. Continued upward pulling on the handle or pull tab will progressively move the bulging section on the internal surface of the beaded flange until the ring portion is clear or free of the beaded flange. A controlled venting is thus provided to thereby minimize the possibility of unwanted popping or blow out of the flexible closure device.
The present invention also provides an improved pull tab in the form of a generally U-shaped strap which is integrally molded with two spaced arms extending from the lever portion and with each strap being of substantial uniform thickness to avoid any abrupt transitions which could form weak points resulting in premature failure of the strap during use.
The foregoing and other advantages of the present invention will become apparent as consideration is given to the following detailed description taken in conjunction with the accompanying drawings wherein: